1. Field of the Invention
The present invention relates to an electric part which is optimally used, e.g., in an automobile, as a vehicle height sensor for detecting a change in vehicle height with a load or a road condition.
2. Description of the Related Art
An electric part of this type, e.g., a vehicle height sensor, is attached to an automobile. As the vehicle height sensor, the following sensor is used. That is, vibration generated by an uneven load is transmitted from wheels to the body through a buffer, and a change in distance between the body and the wheel shaft, i.e., a change in vehicle height, is detected. Some buffer can automatically adjust the vehicle to buffer characteristics corresponding to the change in vehicle height, as shown in FIGS. 14 and 15, a cylindrical portion 1a having opening 1b is formed on a one-end side of a housing 1.
A pivotal shaft 3 having one end projecting from the other-end side of the housing 1, a slider receiver 4 fixed on the other end of the pivotal shaft 3 with calking or the like and built in the housing 1, and a resistor pattern 6a formed on the upper surface of an insulating substrate 6 opposite to the slider receiver 4 are formed printing or the like with reference to a positioning hole 6b. Recessed portions 6c are formed in the outside of the insulating substrate 6.
A pair of snap projections 7a and a pair of snap projections 7b are parallel formed on a holder 7, the snap projections 7a and 7b are attached to be snap-engaged with the recessed portions 6c of the insulating substrate 6. A terminal 8 having one end connected to the resistor pattern 6a by soldering, a lead wire 9 is soldered on the other end of the terminal 8, and a filler 10 for airtightly sealing the interior of the housing 1 is filled in the external end of the opening 1b. In this case, the holder 7 is attached such that the holder 7 is positioned inside the opening 1b and brought into pressure contact with a step portion 1e.
A stepped shaft hole 1d having an other-side cylindrical member 1c communicating with the opening 1b is formed at the shaft center portion of the housing 1. A bearing 11 is formed from the opening 1b onto the step portion of the stepped shaft hole 1d by press fitting or insert molding. The pivotal shaft 3 is pivotally supported by the bearing 11. In the pivotal shaft 3, a spacer 13 is interposed between an E ring 12 and a step portion if on the other-end side of the stepped shaft hole 1d. A sealing 14 is arranged on the outer-end side of the E ring 12 to prevent foreign matter such as mud from entering the housing 1, and the end portion of the stepped shaft hole 1d is covered with a cover 15.
The slider receiver 4 has a slider piece 16 which is in slidable contact with the resistor pattern 6a, and the slider receiver 4 is biased on the insulating substrate 6 by the elastic force of a wavy washer 17. The lead wire 9 soldered on the terminal 8 is lead from the peripheral wall constituting the cylindrical portion 1a on the one-end side of the housing 1 to the outside of the housing 1.
In such an electric part described above, the positioning hole 6b is formed at the central portion of the insulating substrate 6 having the resistor pattern 6a formed thereon. The resistor pattern 6a is printed on the insulating substrate 6 by using a printing mask (not shown) with reference to the positioning hole 6b.
The insulating substrate 6 is fixed on the holder 7 such that the recessed portions 6c formed on the outside of the insulating substrate 6 having the resistor pattern 6a printed thereon are snap-engaged with the plurality of snap projections 7a and 7b formed on the holder 7.
However, the resistor pattern 6a is printed with reference to the positioning hole 6b, and the holder 7 is attached to the insulating substrate 6 having the resistor pattern 6a printer thereon with reference to the outside of the insulating substrate 6. That is, these references are different from each other. For this reason, when the insulating substrate 6 is attached to the holder 7 with reference to the combination between these references, the central position of the holder 7 is offset from the central position of the insulating substrate 6.
Furthermore, since a clearance which is too small to hinder snap engagement is formed between the parallel snap projections 7a and 7b of the holder 7 and the recessed portions 6c on the outside of the insulating substrate 6, when the insulating substrate 6 is attached to the holder 7, instability in y and z directions (see FIG. 15) disadvantageously occurs. For this reason, when the insulating substrate 6 is attached to the holder 7, their errors are accumulated, and precision of the relative position between the slider piece 16 and the resistor pattern 6a cannot be easily held, respective products have large variations in resistance change characteristic.
The terminal 8 is soldered on the resistor pattern 6a, and the lead wire 9 is soldered on the terminal 8. For this reason, a number of portions to be soldered increases to degrade assembling properties.